Hot packs are used to pass heat from the bag to your body while cold ice packs will absorb the excess heat produced by inflammation and pain in the affected area. That's probably why heating bags help you with cramps associated with sports injuries and even for your period. Think of it as a heat exchange that your body likes because it is changing the temperature in your body where it feels the most needed.

A cold ice bag or frozen ice pack seems to help bruises because the affected area's temperature has increased due to the body's reaction to healing the affected area. Cold ice packs help the swelling go down.

Depending on the headache or hangover you have, you may want to try either a cold ice bag or a heated water pack. Generally a frozen ice pack seems to work better at relieving the pain in the area for those pains.

Whether you have a headache hangover, bruises or menstrual pains / cramps will determine if you should use a hot water pack or a .